Conventional Intracranial Pressure Research Articles

Cerebral microcirculation mapped by echo particle tracking velocimetry quantifies the intracranial pressure and detects ischemia

Affecting 1.1‰ of infants, hydrocephalus involves abnormal accumulation of cerebrospinal fluid, resulting in elevated intracranial pressure (ICP). It is the leading cause for brain surgery in newborns, often causing long-term neurologic disabilities or even death. Since conventional invasive ICP monitoring is risky, early neurosurgical interventions could benefit from noninvasive techniques. Here we use clinical contrast-enhanced ultrasound (CEUS) imaging and intravascular microbubble tracking algorithms to map the cerebral blood flow in hydrocephalic pediatric porcine models. Regional microvascular perfusions are quantified by the cerebral microcirculation (CMC) parameter, which accounts for the concentration of micro-vessels and flow velocity in them. Combining CMC with hemodynamic parameters yields functional relationships between cortical micro-perfusion and ICP, with correlation coefficients exceeding 0.85. For cerebral ischemia cases, the nondimensionalized cortical micro-perfusion decreases by an order of magnitude when ICP exceeds 50% of the MAP. These findings suggest that CEUS-based CMC measurement is a plausible noninvasive method for assessing the ICP and detecting ischemia.

Decompressive craniectomy for the treatment of high intracranial pressure in closed traumatic brain injury.

Decompressive craniectomy for the treatment of high intracranial pressure in closed traumatic brain injury.

Fluctuations in intracranial pressure can be estimated non-invasively using near-infrared spectroscopy in non-human primates

Intracranial pressure (ICP) is typically measured invasively through a sensor placed inside the brain or a needle inserted into the spinal canal, limiting the patient population on which this assessment can be performed. Currently, non-invasive methods are limited due to lack of sensitivity and thus only apply to extreme cases of increased ICP, instead of use in general clinical practice. We demonstrate a novel application for near-infrared spectroscopy (NIRS) to accurately estimate ICP changes over time. Using a non-human primate (Rhesus Macaque) model, we collected optical data while we induced ICP oscillations at multiple ICP levels obtained by manipulating the height of a fluid column connected via a catheter to the lateral ventricle. Hemodynamic responses to ICP changes were measured at the occipital pole and compared to changes detected by a conventional intraparenchymal ICP probe. We demonstrate that hemoglobin concentrations are highly correlated with induced ICP oscillations and that this response is frequency dependent. We translated the NIRS data into non-invasive ICP measurements via a fitted non-parametric transfer function, demonstrating a match in both magnitude and time alignment with an invasively measured reference. Our results demonstrate that NIRS has the potential for non-invasive ICP monitoring.

Feature clustering of intracranial pressure time series for alarm function estimation in traumatic brain injury

Objective: The conventional application of intracranial pressure (ICP) monitoring of traumatic brain injury (TBI) patients consists merely in the acquisition of ICP values in discrete time and their comparison to the established ICP threshold. An exceeding of this threshold triggers a special emergency treatment protocol. This paper addresses the possibility of making use of the rich information latent in the ICP records of known vital and fatal outcomes gathered during real clinical practice of treating TBI patients. Our assumption was that the proposed algorithmic procedure derived from this information could, in addition to ICP monitoring itself, provide a complementary added value. This might help clinicians to make better decisions during a patient’s treatment. Approach: We concentrated on studying specific clustering schemes for subsequences of ICP time series. The clusterization problem was formulated for feature vectors which are introduced to represent ICP time subsequences. The ICP transformation to a feature space uses global and local definitions of time subsequences. For clusterization itself, we adopted hierarchical Gaussian mixture models (hGMMs). By using posterior probabilities of the clusters, we introduced three novel alarm functions. We explored two alternative methods of searching for optimum alarm function thresholds (ROC analysis and a novel efficiency measure). Main results: We performed extensive cross-validation experiments on a clinical retrospective data set. The results of the optimization over several hGMMs, various feature space dimensionality and all the types of the novel alarm functions show the potential of the novel alarm functions for supplementing conventional ICP monitoring. Significance: In conclusion, the paper provides a prospective extended ICP monitoring technique for real TBI patients, based on the proposed methodology of ICP subsequence clustering and thresholding of the optimum novel alarm function.

Microdialysis Monitoring in Clinical Traumatic Brain Injury and Its Role in Neuroprotective Drug Development

Injuries to the central nervous system continue to be vast contributors to morbidity and mortality; specifically, traumatic brain injury (TBI) is the most common cause of death during the first four decades of life. Several modalities are used to monitor patients suffering from TBI in order to prevent detrimental secondary injuries. The microdialysis (MD) technique, introduced during the 1990s, presents the treating physician with a robust monitoring tool for brain chemistry in addition to conventional intracranial pressure monitoring. Nevertheless, some limitations remain, such as limited spatial resolution. Moreover, while there have been several attempts to develop new potential pharmacological therapies in TBI, there are currently no available drugs which have shown clinical efficacy that targets the underlying pathophysiology, despite various trials investigating a plethora of pharmaceuticals. Specifically in the brain, MD is able to demonstrate penetration of the drug through the blood-brain barrier into the brain extracellular space at potential site of action. In addition, the downstream effects of drug action can be monitored directly. In the future, clinical MD, together with other monitoring modalities, can identify specific pathological substrates which require tailored treatment strategies for patients suffering from TBI.

Monitoring intracranial pressure utilizing a novel pattern of brain multiparameters in the treatment of severe traumatic brain injury.

The aim of the study was to evaluate the clinical value of multiple brain parameters on monitoring intracranial pressure (ICP) procedures in the therapy of severe traumatic brain injury (sTBI) utilizing mild hypothermia treatment (MHT) alone or a combination strategy with other therapeutic techniques. A total of 62 patients with sTBI (Glasgow Coma Scale score <8) were treated using mild hypothermia alone or mild hypothermia combined with conventional ICP procedures such as dehydration using mannitol, hyperventilation, and decompressive craniectomy. The multiple brain parameters, which included ICP, cerebral perfusion pressure, transcranial Doppler, brain tissue partial pressure of oxygen, and jugular venous oxygen saturation, were detected and analyzed. All of these measures can control the ICP of sTBI patients to a certain extent, but multiparameters associated with brain environment and functions have to be critically monitored simultaneously because some procedures of reducing ICP can cause side effects for long-term recovery in sTBI patients. The result suggested that multimodality monitoring must be performed during the process of mild hypothermia combined with conventional ICP procedures in order to safely target different clinical methods to specific patients who may benefit from an individual therapy.

Randomized Controlled Trial Comparing Cerebral Perfusion Pressure–Targeted Therapy Versus Intracranial Pressure–Targeted Therapy for Raised Intracranial Pressure due to Acute CNS Infections in Children*

In children with acute CNS infection, management of raised intracranial pressure improves mortality and neuromorbidity. We compared cerebral perfusion pressure-targeted approach with the conventional intracranial pressure-targeted approach to treat raised intracranial pressure in these children. Prospective open-label randomized controlled trial. PICU in a tertiary care academic institute. Hundred ten children (1-12 yr) with acute CNS infections having raised intracranial pressure and a modified Glasgow Coma Scale score less than or equal to 8 were enrolled. Patients were randomized to receive either cerebral perfusion pressure-targeted therapy (n = 55) (maintaining cerebral perfusion pressure ≥ 60 mm Hg, using normal saline bolus and vasoactive therapy-dopamine, and if needed noradrenaline) or intracranial pressure-targeted therapy (n = 55) (maintaining intracranial pressure < 20 mm Hg using osmotherapy while ensuring normal blood pressure). The primary outcome was mortality up to 90 days after discharge from PICU. Secondary outcome was modified Glasgow Coma Scale score at 72 hours after enrollment, length of PICU stay, duration of mechanical ventilation, and hearing deficit and functional neurodisability at discharge and 90-day follow-up. A 90-day mortality in intracranial pressure group (38.2%) was significantly higher than cerebral perfusion pressure group (18.2%; relative risk = 2.1; 95% CI, 1.09-4.04; p = 0.020). The cerebral perfusion pressure group in comparison with intracranial pressure group had significantly higher median (interquartile range) modified Glasgow Coma Scale score at 72 hours (10 [8-11] vs 7 [4-9], p < 0.001), shorter length of PICU stay (13 d [10.8-15.2 d] vs. 18 d [14.5-21.5 d], p = 0.002) and mechanical ventilation (7.5 d [5.4-9.6 d] vs. 11.5 d [9.5-13.5 d], p = 0.003), lower prevalence of hearing deficit (8.9% vs 37.1%; relative risk = 0.69; 95% CI, 0.53-0.90; p = 0.005), and neurodisability at discharge from PICU (53.3% vs. 82.9%; relative risk = 0.37; 95% CI, 0.17-0.81; p = 0.005) and 90 days after discharge (37.8% vs. 70.6%; relative risk = 0.47; 95% CI, 0.27-0.83; p = 0.004). Cerebral perfusion pressure-targeted therapy, which relied on more frequent use of vasopressors and lesser use of hyperventilation and osmotherapy, was superior to intracranial pressure-targeted therapy for management of raised intracranial pressure in children with acute CNS infection in reducing mortality and morbidity.

Clinical significance of brain multiparameter monitoring guiding the application of conventional intracranial pressure reducing means in the course of mild hypothermia treatment of severe traumatic brain injury

Objective To analyze and evaluatethe change and clinical significance of brain multiparameter monitoring in guiding the application of conventional intracranial pressure reducing means in the course of mild hypothermia treatment (MHT) of severe traumatic brain injury (sTBI).Methods There were 42 cases in the course of mild hypothermia treatment of severe traumatic brain injury (sTBI).Intracranial pressure (ICP),cerebral perfusion pressure (CPP),brain tissue partial pressure of oxygen (PbtO2),and jugularm venous oxygen saturation (SjvO2) were continuously monitored in 42 cases with sTBI for analyzing the correlations inside.Results 1.Increasing CPP,PbtO2,and SjvO2 were found after the course of MHT for 42 cases with sTBI,and the correlations between each index were closely insides.2.Dehydrating with mannitol in two doses (25 g and 50 g)on ICP ＞ 20 mm Hg,the ICP of two groups of patients were significandy reduced after 30 minutes of treatment.ICP of 25 g group rebounded significantly after 90 min; the 50 g group remained stable at a low level.3.As the degree of hyperventilation deepened,ICP reduction effects were more obvious and the proportion of low PbtO2 also increased.4.ICP decreased in 16 cases of severe brain injury patients after decompressive craniotomy surgery.Furthermore,CPP,PbtO2and SjvO2 increased in varying degrees.Conclusions Continuous monitoring of PbtO2,SjvO2,ICP,and CPP can reflect the close correlations between them.Closely monitoring each index can timely and accurately reflect intracranial condition changes,be used to guide therapy and is of great significance for prognosis. Key words: Traumatic brain injury; Mild hypothermia treatment; Intracranial pressure; Cerebral perfusion pressure ; Brain tissue partial pressure of oxygen

Intracranial pressure and cerebral perfusion pressure monitoring in the preventive nursing care of severe traumatic brain injury

The present study evaluated the roles of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) in preventive nursing care of severe traumatic brain injury (STBI).Totally 100 STBI patients with 3 to 8 Glasgow Coma Score (GCS) score at admission were enrolled in this study, and they were randomly divided into monitoring group (n=50) and control group (n=50). STBI patients were nursed with conventional monitoring in the control group, and STBI patients were nursed with combination of conventional monitoring and ICP and CPP monitoring in the monitoring group, and early treatment and nursing intervention were given according to the monitoring results. Compared with the control group, there was a lower incidence of complications and better curative effects in the monitoring group. The proportion of patients with good curative effects in the monitoring and control group was 64 and 40%, and their mortality rates were 12 and 24%, respectively. Dynamic monitoring of ICP and CPP in the early stage of STBI is conducive to judge the changes of pathogenetic condition and give optimal treatment and early nursing intervention, so it’s an effective measure to reduce disability and mortality rates. Key words: Severe craniocerebral injury, intracranial pressure and cerebral perfusion pressure, monitoring, preventive nursing care.

Detection of Cerebral Compromise With Multimodality Monitoring in Patients With Subarachnoid Hemorrhage

Studies in traumatic brain injury suggest that monitoring techniques such as brain tissue oxygen (P(BTO₂)) and cerebral microdialysis may complement conventional intracranial pressure (ICP) and cerebral perfusion pressure (CPP) measurements. In this study of poor-grade (Hunt and Hess grade IV and V) subarachnoid hemorrhage (SAH) patients, we examined the prevalence of brain hypoxia and brain energy dysfunction in the presence of normal and abnormal ICP and CPP. SAH patients who underwent multimodal neuromonitoring and cerebral microdialysis were studied. We examined the frequency of brain hypoxia and energy dysfunction in different ICP and CPP ranges and the relationship between P(BTO₂) and the lactate/pyruvate ratio (LPR). A total of 2394 samples from 19 patients were analyzed. There were 149 samples with severe brain hypoxia (P(BTO₂) ≤10 mm Hg) and 347 samples with brain energy dysfunction (LPR >40). The sensitivities of abnormal ICP or CPP for elevated LPR and reduced P(BTO₂) were poor (21.2% at best), and the LPR or P(BTO₂) was abnormal in many instances when ICP or CPP was normal. Severe brain hypoxia was often associated with an LPR greater than 40 (86% of samples). In contrast, mild brain hypoxia (≤20 mm Hg) and severe brain hypoxia were observed in only 53% and 36% of samples with brain energy dysfunction, respectively. Our data demonstrate that ICP and CPP monitoring may not always detect episodes of cerebral compromise in SAH patients. Our data suggest that several complementary monitors may be needed to optimize the care of poor-grade SAH patients.

Brain tissue oxygen–directed management and outcome in patients with severe traumatic brain injury

The object of this study was to determine whether brain tissue oxygen (PbtO(2))-based therapy or intracranial pressure (ICP)/cerebral perfusion pressure (CPP)-based therapy is associated with improved patient outcome after severe traumatic brain injury (TBI). Seventy patients with severe TBI (postresuscitation GCS score < or = 8), admitted to a neurosurgical intensive care unit at a university-based Level I trauma center and tertiary care hospital and managed with an ICP and PbtO(2) monitor (mean age 40 +/- 19 years [SD]) were compared with 53 historical controls who received only an ICP monitor (mean age 43 +/- 18 years). Therapy for both patient groups was aimed to maintain ICP < 20 mm Hg and CPP > 60 mm Hg. Patients with PbtO(2) monitors also had therapy to maintain PbtO(2) > 20 mm Hg. Data were obtained from 12,148 hours of continuous ICP monitoring and 6,816 hours of continuous PbtO(2) monitoring. The mean daily ICP and CPP and the frequency of elevated ICP (> 20 mm Hg) or suboptimal CPP (< 60 mm Hg) episodes were similar in each group. The mortality rate was significantly lower in patients who received PbtO(2)-directed care (25.7%) than in those who received conventional ICP and CPP-based therapy (45.3%, p < 0.05). Overall, 40% of patients receiving ICP/CPP-guided management and 64.3% of those receiving PbtO(2)-guided management had a favorable short-term outcome (p = 0.01). Among patients who received PbtO(2)-directed therapy, mortality was associated with lower mean daily PbtO(2) (p < 0.05), longer durations of compromised brain oxygen (PbtO(2) < 20 mm Hg, p = 0.013) and brain hypoxia (PbtO(2) < 15 mm Hg, p = 0.001), more episodes and a longer cumulative duration of compromised PbtO(2) (p < 0.001), and less successful treatment of compromised PbtO(2) (p = 0.03). These results suggest that PbtO(2)-based therapy, particularly when compromised PbtO(2) can be corrected, may be associated with reduced patient mortality and improved patient outcome after severe TBI.

Advances in brain tissue oxygen monitoring: Using the Licox system in neurointensive care

The care and management of a traumatic brain-injured patient continues to present many challenges to the bedside practitioner. As technology is integrated into intensive care management it has become clear that maintaining conventional intracranial pressure and cerebral perfusion pressure levels will not always prevent cerebral ischaemia. The Licox Brain Tissue Oxygen Monitoring System offers a direct, accurate, real-time, regional partial pressure measurement of oxygen levels in brain tissue. The information gained from this monitoring system will provide an early warning of oxygenation problems that can contribute to secondary injury. When Licox is used in combination with other neurointensive care monitoring parameters it can help inform the bedside practitioner in making decisions about the choice of interventions and in assessing their effectiveness.

Conventional neurocritical care and cerebral oxygenation after traumatic brain injury

Control of intracranial pressure (ICP) and cerebral perfusion pressure (CPP) is the foundation of traumatic brain injury (TBI) management. In this study, the authors examined whether conventional ICP- and CPP-guided neurocritical care ensures adequate brain tissue O2 in the first 6 hours after resuscitation. Resuscitated patients with severe TBI (Glasgow Coma Scale score < or = 8 and Injury Severity Scale score > or = 16) who were admitted to a Level I trauma center and who underwent brain tissue O2 monitoring within 6 hours of injury were evaluated as part of a prospective observational database. Therapy was directed to maintain an ICP of 25 mm Hg or less and a CPP of 60 mm Hg or higher. Data from a group of 25 patients that included 19 men and six women (mean age 39 +/- 20 years) were examined. After resuscitation, ICP was 25 mm Hg or less in 84% and CPP was 60 mm Hg or greater in 88% of the patients. Brain O2 probes were allowed to stabilize; the initial brain tissue O2 level was 25 mm Hg or less in 68% of the patients, 20 mm Hg or less in 56%, and 10 mm Hg or less in 36%. Nearly one third (29%) of patients with ICP readings of 25 mm Hg or less and 27% with CPP levels of 60 mm Hg or greater had severe cerebral hypoxia (brain tissue O2 < or = 10 mm Hg). Nineteen patients had both optimal ICP (< 25 mm Hg) and CPP (> 60 mm Hg); brain tissue O2 was 20 mm Hg or less in 47% and 10 mm Hg or less in 21% of these patients. The mortality rate was higher in patients with reduced brain tissue O2. Brain resuscitation based on current neurocritical care standards (that is, control of ICP and CPP) does not prevent cerebral hypoxia in some patients. This finding may help explain why secondary neuronal injury occurs in some patients with adequate CPP and suggests that the definition of adequate brain resuscitation after TBI may need to be reconsidered.

Reduced mortality rate in patients with severe traumatic brain injury treated with brain tissue oxygen monitoring

An intracranial pressure (ICP) monitor, from which cerebral perfusion pressure (CPP) is estimated, is recommended in the care of severe traumatic brain injury (TBI). Nevertheless, optimal ICP and CPP management may not always prevent cerebral ischemia, which adversely influences patient outcome. The authors therefore determined whether the addition of a brain tissue oxygen tension (PO2) monitor in the treatment of TBI was associated with an improved patient outcome. Patients with severe TBI (Glasgow Coma Scale [GCS] score < 8) who had been admitted to a Level I trauma center were evaluated as part of a prospective observational database. Patients treated with ICP and brain tissue PO2 monitoring were compared with historical controls matched for age, pathological features, admission GCS score, and Injury Severity Score who had undergone ICP monitoring alone. Therapy in both patient groups was aimed at maintaining an ICP less than 20 mm Hg and a CPP greater than 60 mm Hg. Among patients whose brain tissue PO2 was monitored, oxygenation was maintained at levels greater than 25 mm Hg. Twenty-five patients with a mean age of 44 +/- 14 years were treated using an ICP monitor alone. Twenty-eight patients with a mean age of 38 +/- 18 years underwent brain tissue PO2-directed care. The mean daily ICP and CPP levels were similar in each group. The mortality rate in patients treated using conventional ICP and CPP management was 44%. Patients who also underwent brain tissue PO2 monitoring had a significantly reduced mortality rate of 25% (p < 0.05). The use of both ICP and brain tissue PO2 monitors and therapy directed at brain tissue PO2 is associated with reduced patient death following severe TBI.

Ophthalmodynamometrie

Central vein pressure depends on intracranial pressure (ICP). Baurmann in 1925 therefore recommended measuring central vein pressure to determine ICP, but the accuracy of this method has not yet been verified. To test the method we measured venous outflow pressure (VOP) by noninvasive ophthalmodynamometry (ODM). We studied 31 patients with suspected increased ICP. ICP was recorded continuously for a minimum of 24 h by intraventricular catheters, and ODM was performed during ICP measurement. The findings were compared with the results of conventional invasive ICP measurement. Pressure in the central retinal vein was highly correlated with ICP. Measuring VOP by ODM seems to be a reliable method for noninvasive recording of ICP. It is a useful screening test in all cases of presumed ICP elevation.

Moderate hypothermia in patients with severe head injury: cerebral and extracerebral effects.

Cerebral and extracerebral effects of moderate hypothermia (core temperature 32.5 degrees C-33.0 degrees C) were prospectively studied in 10 patients with severe closed head injury (Glasgow Coma Scale score < 7) in the intensive care unit of a university hospital. Hypothermia was induced by cooling the patient's body surface with water-circulating blankets. Before cooling, a conventional intracranial pressure (ICP) reduction therapy was applied, which remained unchanged throughout the study. Cerebral blood flow (CBF), cerebral metabolic rates for oxygen (CMRO2) and lactate (CMRL), and ICP were simultaneously measured prior to inducing hypothermia, after obtaining hypothermia, after 24 hours of hypothermia, and after rewarming. With respect to extracerebral effects, supplemental investigations were conducted 24 and 72 hours after rewarming. The median delay between injury and induction of hypothermia was 16 hours. Hypothermia reduced CMRO2 by 45% (p < 0.01), whereas CBF did not change significantly. Before cooling, six patients had elevated CMRL indicating cerebral ischemia. Cooling normalized CMRL in all patients (p < 0.01). The intracranial hypertension present prior to cooling declined markedly during hypothermia (p < 0.01) without significant rebound effects after rewarming. Cardiac index decreased by 18% after hypothermia was reached (p < 0.05), recovered at 24 hours of hypothermia, and surpassed baseline values after rewarming. Platelet counts dropped continuously up to 24 hours after rewarming (p < 0.01). Plasma coagulation tests did not show significant worsening. Creatinine clearance decreased during cooling (p < 0.01) and recovered by 24 hours after rewarming. Twenty-four hours after cooling had begun, eight patients had elevated serum lipase activity (p < 0.01) and four of them acquired pancreatitis. Rewarming normalized both pancreatic alterations. Seven patients made a good recovery; one survived severely disabled; and two patients died. Moderate hypothermia is effective in preventing secondary brain damage while reducing cerebral ischemia. However, there are potentially hazardous side effects that require additional monitoring.